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EP-4735779-A1 - GAS SPRING

EP4735779A1EP 4735779 A1EP4735779 A1EP 4735779A1EP-4735779-A1

Abstract

A gas spring (1) comprising: an outer casing (2) internally provided with a closed cavity (3); a piston-rod (4) which is fitted in the outer casing (2) in axially slidable manner and is structured so as to form/ delimit, inside said closed cavity (3), a variable- volume closed chamber adapted to contain a pressurized gas; and one or more annular gaskets (7, 10, 11) that are interposed between the piston-rod (4) and the outer casing (2) and/or between separate pieces (5, 6) of the outer casing (2) and at least one of which is made of a graphite-filled and/or carbon fibre-filled polymeric material.

Inventors

  • CAPPELLER, AUGUSTO
  • FIORESE, MASSIMO
  • GUSELLA, Giovanni

Assignees

  • Special Springs S.r.l.

Dates

Publication Date
20260506
Application Date
20240627

Claims (11)

  1. 1. A gas spring (1) comprising: an outer casing (2) internally provided with a closed cavity (3) ; a piston-rod (4) , which is fitted in the outer casing (2) in axially slidable manner and is structured so as to form/delimit , inside said closed cavity (3) , a variable-volume closed chamber adapted to contain a pressurized gas; and one or more annular gaskets (7, 10, 11) that are interposed between the piston-rod (4) and the outer casing (2) and/or between separate pieces (5, 6) of the outer casing (2) ; said gas spring (1) being characterised in that at least one of said annular gaskets (7, 10, 11) is made of a graphite- filled and/or carbon fibre-filled polymeric material.
  2. 2. The gas spring according to Claim 1, wherein said polymeric material is an elastomer.
  3. 3. The gas spring according to Claim 1 or 2, wherein said polymeric material is a polyurethane.
  4. 4. The gas spring according to any one of the preceding claims, wherein the amount of graphite and/or carbon fibre is lower than 20% by weight of the polymeric material.
  5. 5. The gas spring according to any one of the preceding claims, wherein the amount of graphite and/or carbon fibre is lower than 10% by weight of the polymeric material.
  6. 6. The gas spring according to any one of the preceding claims, wherein the amount of graphite and/or carbon fibre is higher than 0,5% by weight of the polymeric material.
  7. 7. The gas spring according to any one of the preceding claims, wherein the quantity of graphite and/or carbon fibre is higher than 1% by weight of the polymeric material.
  8. 8. The gas spring according to any one of the preceding claims, wherein said annular gasket or gaskets (7, 10, 11) has/have a surface hardness higher than or equal to 90 ShoreA.
  9. 9. The gas spring according to any one of the preceding claims, wherein said annular gasket or gaskets (7, 10, 11) is/are annular sealing gaskets and/or protective annular gaskets .
  10. 10. The gas spring according to any one of the preceding claims, wherein said annular gasket or gaskets (7, 10, 11) is/are single lip or double lip annular gasket (s) .
  11. 11. The gas spring according to any one of the preceding claims, wherein the outer casing (2) comprises a cup-shaped body (5) and a plug body (6) , separate and distinct from the cup-shaped body (5) , which is at least partially fitted into the cup-shaped body (5) , so as to delimit said closed cavity (3) ; said plug body (6) being coupled f luid-tightly to said cup-shaped body (5) via the interposition of at least one of said annular gaskets (7) .

Description

GAS SPRING CROSS-REFERENCE TO RELATED APPLICATIONS This Patent Application claims priority from Italian Patent Application No . 102023000013392 filed on June 28 , 2023 , the entire disclosure of which is incorporated herein by reference . TECHNICAL FIELD The present invention relates to a gas spring . More in detail , the present invention relates to a gas spring adapted to be used in the field of sheet metal forming . Use to which the following disclosure will make explicit reference without thereby losing generality . BACKGROUND OF THE INVENTION As is known, the gas springs that are used in the dies for sheet metal forming general ly comprise : a cup-shaped body substantially cylindrical in shape ; a guide bushing, separate and distinct from the cup-shaped body, which fluid- tightly closes the mouth of the cup-shaped body via the interposition of a series of annular sealing gaskets ; and a substantially cylindrical-shaped, piston-rod which is fitted in pass-through and axially slidable manner in the hole at centre of the guide bushing, so as to be able to move axially with respect to the cup-shaped body between a retracted position and an extracted or extended position . The piston- rod is moreover fitted f luid-tightly into the guide bushing, so as to form/delimit , together with the cup-shaped body and the guide bushing, a variable-volume closed chamber that is filled up with a high-pressure gas . Clearly, a series of annular sealing gaskets , usually made of polymeric material , are moreover interposed between the cup-shaped body and the guide bushing and/or between the guide bushing and the piston-rod . The high-pressure gas keeps the piston-rod in the completely extended or extracted position, i . e . with the inner end of the piston-rod in abutment on the guide bushing, until the piston-rod undergoes an axial force capable of overcoming the thrust of the gas . In the gas springs most widespread on the market , the nominal gas pressure inside the variable-volume closed chamber ( i . e . the gas pressure with the piston-rod in the completely extended or extracted position) usually ranges between 20 and 200 bar . As a result , during normal operation of the gas spring the gas pressure inside the variable-volume closed chamber can rise up to easily reach values above 500- 600 bar, with sealing problems that this entails . Having to prevent the leakage of pressuri zed gas with such high pressure di fferences , in fact , the annular sealing gaskets are the components of the gas spring that are mostly stressed and subj ect to breakage , and therefore they condition the average li fe of the component . SUMMARY OF THE INVENTION Aim of the present invention is to reali ze annular sealing gaskets that can extend the average li fe of the gas springs , without excessively increasing the production costs thereof . In accordance with these aims , according to the present invention there i s provided a gas spring as defined in Claim 1 and preferably, though not neces sarily, in any one of the claims depending on it . BRIEF DESCRIPTION OF THE DRAWINGS The present invention will now be described with reference to the attached drawings , which show a non-limiting embodiment thereof , wherein : - Figure 1 is a perspective view o f a gas spring reali zed according to the teachings of the present invention, with parts removed for clarity ' s sake ; - Figure 2 is a side view of the gas spring shown in Figure 1 , sectioned along the midplane and with parts removed for clarity ' s sake ; whereas - Figure 3 is a side view of a second embodiment of the gas spring shown in Figure 1 , sectioned along the midplane and with parts removed for clarity ' s sake . DETAILED DESCRIPTION OF THE EMBODIMENTS With reference to Figures 1 and 2 , number 1 denotes as a whole a gas spring that can be advantageously used in the presses or dies for the cold forming of metal sheets and the like . The gas spring 1 comprises : an outer casing 2 with a rigid and sel f-supporting structure , which is internally provided with a large closed cavity 3 advantageously complementary in shape , which is insulated from the outside ; and an oblong-shaped piston-rod 4 , which is fitted in the outer casing 2 in axially slidable and fluid-tight manner, so as to protrude cantilevered outside of the casing 2 , and is shaped/ structured so as to form/delimit , inside and together with the inner cavity 3 of casing 2 , a variablevolume closed chamber that contains/ is adapted to contain nitrogen or other pressuri zed gas . Clearly, the pressuri zed gas present inside the closed cavity 3 , or rather inside the variable-volume closed chamber, has a pressure higher than the external one so as to maximi ze the volume of the closed chamber . More in detail , the piston-rod 4 is fitted in axially slidable manner in a substantially complementary-shaped straight hole , which is made in the outer casing 2 so as to connect the cavity 3 directly with the outside . In add